JPH04120131A - Production of organopolysiloxane - Google Patents

Abstract

PURPOSE:To obtain the subject compound having high quality by reacting a specific compound to an organopolysiloxane obtained by the equilibration reaction in the presence of an alkali catalyst, thereby easily silylating and sealing the residual silanol group at a high ratio. CONSTITUTION:An organopolysiloxane is produced by equilibrating an organocyclopolysiloxane in the presence of an alkali catalyst (preferably a tetraalkylphosphonium hydroxide, etc.) under heating. The silanol group in the organopolysiloxane is silylated and sealed by the addition reaction of a silyl ketene acetal compound having the group of formula (R is univalent organic group) to the above organopolysiloxane. The silylation reaction of the silanol group is carried out preferably at 80-120 deg.C by adding 2-3 times mol of the silyl ketene acetal compound based on the theoretical molar number of the residual silanol group.

Description

Detailed Description of the Invention The present invention provides a high rate of silylation and sealing of silanol groups produced when organopolysiloxane is obtained by equilibration reaction of organocyclopolysiloxane in the presence of an alkali catalyst. The present invention relates to a method for producing an organopolysiloxane that is stable and of high quality and can be suitably used as a potting agent, adhesive, etc. in the electrical and electronic fields.

Conventionally, organopolysiloxanes have been produced by using organocyclopolysiloxanes with alkali catalysts, such as sodium hydroxide, potassium hydroxide, cesium hydroxide, tetraalkylphosphonium hydroxide, tetraalkyl hydroxide, etc. A method of producing by heating and equilibrating in the presence of ammonium hydroxide or these syralate compounds is known, but in this reaction,
Silanol groups are generated due to the incorporation of hydroxyl groups or water, and the remaining amount thereof is usually several hundred to several thousand ppm. This residual silanol group is chemically unstable,
Since this adversely affects the heat resistance of organopolysiloxane, it is desirable to perform a sealing treatment.

In the second case, it is widely known that silylation reactions are used to improve the stability of chemically unstable substances; for example, alcoholic hydroxyl groups can be removed using trialkylchlorosilane or hexaalkyldisilazane. silylated. However, in the case of silylation using trialkychlorosilane, it is necessary to use a dehydrochlorination agent such as a tertiary amine or pyridine in order to remove the hydrochloric acid by-produced when the reaction is completed. If the reaction is slow and takes a long time to complete, it is necessary to add an acid catalyst such as trifluoroacetic acid.

Therefore, in the above-mentioned silylation reaction, it was necessary to add a special step to remove the dehydrochlorination agent and the acid catalyst at the end of the reaction.

Therefore, in order to block the silanol groups of the organopolysiloxane produced by equilibration reaction in the presence of the above-mentioned alkali catalyst, it is possible to silylate and block the organopolysiloxane using trialkylchlorosilane or hexaalkyldisilazane to improve the stability. However, with this method, the product must be washed with water after sealing treatment, and then heated and depressurized to distill off the dehydrochloric agent and acid catalyst, so the process is cumbersome, and the sealing rate is not satisfactory. Moreover, when the acid catalyst is in excess, there is also the disadvantage that the organopolysiloxane is cracked.

Furthermore, Japanese Patent Publication No. 12931/1983 proposes a method of silylation by simultaneously adding hexaorganosilazane and triorganochlorosilane, but this method seals the silanol groups of organopolysiloxane. However, a filtration process is required to remove the salts produced, and especially in the production of highly viscous organopolysiloxanes, a large amount of process time is required, and the sealing rate is far from sufficient. there were.

Furthermore, no matter which method is used for silylation,
Since salt is essentially produced, there is a risk that ionic impurities may be mixed into the target organopolysiloxane unless sufficient care is taken during production. Contamination with such impurities is caused by potting agents,
This can be a fatal defect for organopolysiloxanes, which are widely used as adhesives, and is extremely disadvantageous industrially.

As described above, when an organopolysiloxane is produced by performing an equilibration reaction in the presence of an alkali catalyst, it has been difficult to silylate and seal the remaining silanol groups in an industrially advantageous manner using conventional methods.

The present invention was made in view of the above circumstances, and is an organopolysiloxane that can obtain stable and high-quality organopolysiloxane by silylating residual silanol groups with a simple operation and a high sealing rate. An object of the present invention is to provide a method for producing siloxane.

As a result of extensive studies to achieve the above object, the inventors of the present invention heated and equilibrated organocyclopolysiloxane in the presence of an alkali catalyst to obtain an organopolysiloxane. By adding and reacting a silylketene acecool compound containing at least one group represented by formula (1) (wherein R is a monovalent organic group) in the molecule, the silyl ketene acecool compound remaining in the organopolysiloxane is The silanol group is easily silylated without the addition of a catalyst, and since there are no by-products during salt removal, there is no need to remove by-product salts, which greatly simplifies the process. The silanol groups of organopolysiloxane can be silylated and capped at a high rate without fear of contamination, and therefore, the silanol groups can be silylated and capped with a simple operation and at a high sealing rate. It was discovered that organopolysiloxane, which is stable and of high quality and can be suitably used as potting agents, adhesives, etc. in the electrical and electronic fields, can be produced industrially advantageously, and the present invention was accomplished.

Therefore, the present invention provides a method for producing organopolysiloxane by heating and equilibrating organocyclopolysiloxane in the presence of an alkali catalyst. Provided is a method for producing an organopolysiloxane, which comprises adding and reacting a silylketene acecool compound containing at least one group represented by the above formula (1) in the molecule to block the silanol group by silylation. .

The present invention will be explained in more detail below.

In the production method of the present invention, an alkali catalyst is first added to an organocyclopolysiloxane by a conventional method, and the mixture is heated and equilibrated to obtain an organopolysiloxane.

Here, the organone chloropolysiloxane as a starting material may be used, for example, by the following general formula "where R' is each independently a hydrogen atom or an unsubstituted or substituted carbon atom having 1 to 10, preferably 1 to 8 carbon atoms.
A valent hydrocarbon group, such as an alkyl group such as a methyl group, an ethyl group, a propyl group, or a methyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group, an aryl group such as a phenyl group or a tolyl group, a benzyl group, Aralkyl groups such as phenylethyl groups, or chloromethyl groups and chloropropyl groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc., 3,3.
3-) Substituted hydrocarbon groups such as a refluoropropyl group and a 2-cyanoethyl group are exemplified. Further, n represents an integer of 3 to 10, preferably 3 or 4. ” are preferably used.

In this case, in order to adjust the degree of polymerization of the organopolysiloxane, a polymerization chain terminator such as hexamethyldisiloxane or tetramethyldivinyldisiloxane may be added together with the organocyclopolysiloxane. The amount added can be appropriately selected and adjusted to a desired degree of polymerization by adjusting the molar ratio of the R'zSiO units of the organocyclopolysiloxane and the polymerization chain terminator.

Further, examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, cesium hydroxide, tetraalkylphosphonium hydroxide, tetraalkylammonium hydroxide, and syralate compounds thereof. In particular, when tetraalkylphosphonium hydroxide, tetraalkylammonium hydroxide, and their syralate compounds are used as an alkali catalyst, the alkali catalyst itself becomes 15
Since it is decomposed by heating to about 0''C, it is not necessary to add and remove a neutralizing agent after the reaction, which is preferable.

Note that the amount of the alkali catalyst added can be a catalytic amount, and is usually 0.1 per mole of organopolysiloxane.
~0.01 mol%.

The conditions for the above-mentioned equilibration reaction can be normal conditions,
For example, it is possible to adopt conditions of heating to 90 to 150°C and reacting for 2 to 10 hours.

After equilibration, if necessary, an acid such as tricresyl phosphate or ethylene chlorohydrin may be added as a neutralizing agent to neutralize the remaining alkali catalyst.

Therefore, in the present invention, the organopolysiloxane obtained by the above method contains at least one group represented by the following formula (1) (wherein R is a monovalent organic group) in the molecule. A silylketene acecool compound is added and reacted.

Here, R in the above formula (1) is, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a vinyl group,
Alkenyl groups such as allyl groups and butenyl groups, phenyl groups,
Oryl groups such as tolyl groups, aralkyl groups such as benzyl groups, 2-phenylethyl groups, and those in which some of these hydrogen atoms are substituted with halogen atoms, such as chloromethyl groups,
1 to 10 carbon atoms such as 3,3.3 trifluoropropyl group
a substituted or unsubstituted-valent hydrocarbon group, and further 105iR:+
Examples include "groups (R'" is a monovalent hydrocarbon group as exemplified above).

Typically, a compound represented by the following formula (2) can be used as the silylketene acecool compound.

(However, in the formula, R' and R2 are hydrogen atoms or unsubstituted or substituted monovalent hydrocarbon groups similar to R as exemplified above, R3
is an unsubstituted or substituted monovalent hydrocarbon group similar to R or -R
'-5iR,' represents a group (R' is an alkylene group, R5 is an alkoxy group or a monovalent hydrocarbon group similar to R). ) Specific examples of such silylketene acetal compounds include compounds of the following formula.

The above silyl ketene acetal compound can be easily synthesized, for example, by reacting diisopropylamine lithium represented by the following formula (2) and then reacting it with halosilane (see the reaction formula below).Also, the silyl ketene acetal compound can also be obtained by adding hydrogen silane or siloxane to methacrylic ester in the presence of a Wilkinson complex, and specifically can be synthesized according to the reaction formula below.

Here, the methacrylic ester, hydrogen silane or siloxane used is appropriate for the desired silylketene acetal compound.

In the present invention, the silyl ketene acetal compound silylates a silanol group according to the reaction formula below, and at this time, an ester compound is produced as a reaction by-product.

This ester compound is easily removed by a vacuum heating step in the normal manufacturing process of organopolysiloxane, and since the ester compound is neutral, there is no formation of salts, and the ester compound is dissolved in the organopolysiloxane. No ionic impurities remain.

Here, in the silylation reaction of silanol groups using a silyl ketene acecool compound, the amount of the silyl ketene acetal compound is usually equal to or more than 2 to 3 times the theoretical molar amount of residual silanol groups in the produced organopolysiloxane. molar addition, from room temperature to 150” C1 especially 80
It can be carried out at temperatures of ~120°C. in this case,
The reaction time is usually 1 to 5 hours.

Note that after the silylation reaction, when the ester compound is subjected to heating stripping under reduced pressure, a conventional method can be used.

According to the method for producing organopolysiloxane of the present invention,
A stable and high-quality organopolysiloxane can be industrially advantageously obtained by silylating and sealing silanol groups with a simple operation and a high sealing rate. Furthermore, the organopolysiloxane obtained by the method of the present invention is free from the possibility of contamination with ionic impurities, and can be suitably used as potting agents, adhesives, etc. in the electrical and electronic fields.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] 0.7 g of tetrabutylphosphonium hydroxide was added to a mixture consisting of 2 g of 1,3-divinyl-1,1,3,3,-tetramethyldisiloxane and 600 g of octamethylcyclotetrasiloxane. , 110″
The reaction was carried out at C for 4 hours.

When this reaction solution was heated at 150°C for 2 hours to decompose the catalyst and neutralize it, the viscosity at 25°C was 3000.
A silicone oil with a silanol content of 400 ppm was obtained at 0 cst.

Next, 1.2 g of a compound represented by the following formula was added to 100 g of this silicone oil, and the mixture was reacted at 100°C for 1 hour. After this, stripping was carried out for 10 hours under a reduced pressure of 200°C/0.1 torr, and a transparent silicone oil with no turbidity was obtained.

The silanol content of this product was 80 ppm.

[Example 2] 2400 g of octamethylcyclotetrasiloxane and 1
．． 2,3.4. -tetravinyl-1,2,3゜A mixture consisting of 2 g of 4-tetramethylcyclotetrasiloxane and 6 g of hexamethyldisiloxane was heated for 11 hours under nitrogen gas aeration.
After dehydration at 0°C for 2 hours, cool to 80°C.
(C4H9) 1.2g of aPOH was added and reacted at 140°C for 16 hours. When this reaction solution was heated at 150°C for 3 hours to deactivate the catalyst, an oil with a viscosity of 15,000 cp at 25°C was obtained.

The silanol group content of this oil was 500 ppm.

Next, 3 g of a compound represented by the following formula was added to 300 g of this oil, and the mixture was reacted at 100'C for 1.5 hours.After this, the temperature was increased to 200'C/1 torr.
After stripping for 10 hours under reduced pressure, a transparent silicone oil with no turbidity was obtained.

The silanol group content of this product was 75 ppm.

[Example 3] A mixture consisting of 140 g of octaphenylcyclotetrasiloxane and 1700 g of octamethylcyclotetrasiloxane was dehydrated at 110"C/2 hours under nitrogen aeration, then cooled to 80°C, and divinyltetramethyldisiloxane was dehydrated. Add 75g of Siloxa and 2.2g of (C4H9)4POH,
The reaction was carried out at 150°C for 200 hours. This reaction solution was heated to 140 ml.
When the catalyst was deactivated by heating at °C for 3 hours, 25 °C
An oil having a viscosity at C of 20,000 cp was obtained. The silanol group content of this oil was 500 ppm.

Next, 20 g of a compound represented by the following formula was added to 2000 g of this oil, and the mixture was reacted at 100°C for 3 hours. After this, it was heated at 200 °C / 0.1 torr for 15 minutes.
When time stripping was carried out, a clear silicone oil with no turbidity was obtained.

The silanol group content of this product was 120 ppm.

Applicant: Shin-Etsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. In a method for producing an organopolysiloxane by heating and equilibrating organocyclopolysiloxane in the presence of an alkali catalyst, the organopolysiloxane is Siloxane contains at least one group represented by the following formula (1) ▲Mathematical formula, chemical formula, table, etc.▼...(1) (However, in the formula, R is a monovalent organic group.) Contains at least one group in the molecule. A method for producing an organopolysiloxane, which comprises adding and reacting a silylketene acetal compound to silylate and block the silanol groups.